I am populating a JComboBox (using addItem()) with all the elements of a collection. Each element in the collection is a HashMap (so its a ComboBox of Hashmaps..). My question is - Given that I need each item to be a HashMap how do I set the text to apear in the combobox on the GUI? It needs to be the value of a certain key in the map...
I was wondering how Java orders items in the Map (HashMap or Hashtable) when they are added. Are the keys ordered by the hashcode, memory reference or by allocation precedence...? It's because I've noticed same pairs in the Map are not always in the same order ...
I'm not sure how I use get() to get my information. Looking at my book, they pass the key to get(). I thought that get() returns the object associated with that key looking at the documentation. But I must be doing something wrong here.... Any thoughts? import java.util.*; public class OrganizeThis { /** Add a person to t...
I'm looking for a good hash map implementation. Specifically, one that's good for creating a large number of maps, most of them small. So memory is an issue. It should be thread-safe (though losing the odd put might be an OK compromise in return for better performance), and fast for both get and put. And I'd also like the moon on a stick...
hi everyone, i have a parent class called Course, and two child class PostgradCourse and UndergradCourse. i have a hashmap HashMap courses; i store all the postgradCourse and undergradCourse objects in the hashmap. i want to retrieve an undergradCourse object from the hashmap using the key. Course course = courses.get(courseCode); t...
I'm working with the latest draft of the twitter annotations api. An example bit of data looks like status { annotations : [ {myAnnotationType:{myKey:myValue}}, {someoneElsesAnnotationType:{theirKey:theirValue}}, ] } now i want to check a status to see if it has an annotation with myAnnotationType in it. I...
HashMap allows one null key and any number of null values. what is the use of it? ...
I am writing this little Lottery application. Now the plan is, to count how often each number has been drawn during each iteration of the Lottery, and store this somewhere. My guess is that I would need to use a HashMap, that has 6 keys and increments the value by one everytime the respective keys number is drawn. But how would I acco...
else if (!registryData.ContainsKey(keyName)) { keyInvolved = new RegistryKy(keyName); lock (registryDataLock) { registryData.Add(keyName, keyInvolved); } processInvolved = new Proces(procInvolved); keyInvolved.addProcessToDict(processInvolved); } keyName is a String which represents a registry key. keyIn...
can some one please explain what is happening in the code below and how it ends up with 36? thanks edit by Amir Rachum public class HashMap2009 { public static void main (String[] args) { Map<String, Integer> myMap2009 = new HashMap<String, Integer>(); myMap2009.put("one", new Integer(1)); myM...
Hi! For readability reasons I'm trying to avoid using Char based case constructs, using Java 6. I cannot switch to 7 jet... Map<String, String> map = new HashMap<String, String>() { { put("foo", "--foo"); put("bar), "--bar"); ... } private static final long serialVersionUID = 1L; // java pr...
I often have a need to take a list of objects and group them into a Map based on a value contained in the object. Eg. take a list of Users and group by Country. My code for this usually looks like: Map<String, List<User>> usersByCountry = new HashMap<String, List<User>>(); for(User user : listOfUsers) { if(usersByCountry.containsKe...
If LinkedHashMap's time complexity is same as HashMap's complexity why do we need HashMap? What are all the extra overhead LinkedHashMap has when compared to HashMap in Java? ...
I'm profiling some old java code and it appears that my caching of values using a static HashMap and a access method does not work. Caching code (a bit abstracted): static HashMap<Key, Value> cache = new HashMap<Key, Value>(); public static Value getValue(Key key){ System.out.println("cache size="+ cache.size()); ...
I am using hash_map in application as typedef hash_map<DWORD,CComPtr<IInterfaceXX>> MapDword2Interface; In main application I am using static instance of this map static MapDword2Interface m_mapDword2Interface; I have got one crash dump from one of the client machines which point to the crash in clearing this map I opened that cra...
I have check out this Wikipedia page on it, but I still don't understand it. Can someone please help my dim-witted mind to understand the concepts of hashing, hashtable/hashmap, and hash functions? Some examples would really help. ...
Possible Duplicate: How to sort a Map<Key, Value> on the values in Java? I have a HashMap of the type: HashMap<String, Integer> h = new HashMap<String, Integer>(); The HashMap contains a list of Strings and the Integer is a counter for the number of times that String has been found. What I would like to be able to do is sor...
I have to create a lookup table for C function names (as keys) to function pointers (as values). I am thinking of using STL's hash_map container, as the access time of a hash table is O(1). Is there any good hash function for this? Currently I am using (31*H + c) as my hash function. Also, does STL's hash_map takes care of collisions, o...
I have a hash object from an ActiveRecord. I'm going to be calling to_json on it, but I am looking to reduce the depth of the object that is being returned. Here is what my find looks like: @tags = Tag.find_all_by_type("some_type", :select => :name) The result of @tags.to_json looks like this: [{"tag": {"name": "some tag name"}}, ...
I have a database with 2 tables CD and Song. Session bean access then entity classes of those two tables. In my backing bean, I just have a String cd and HashMap<CDName, CDName> cds that will hold the list of CD return back from my sessionbean, so in JSF I would do something like this. <h:selectOneMenu id="cd" value="#{backingBean.cd}"...